The person you are dating tells you that they want you to strip them down and tie them to a bed and whip them with an object of your choice, what do

I'd try it with a belt if I didn't have anything more suited at the moment. It's something I always wanted to do to a girl but honestly I don't know if I could commit and really get into it without feeling guilty or like I was doing something wrong so I might have to ask even though I'd hate every second of it that she do the same to me to make up for it.